A disposable sterilized syringe is a new medical instrument introduced to China in 1980s, which may avoid cross-infection and is easy to use, thus is very popular with doctors and patients. However, due to mismanagement of some medical institutions or interest drive, the disposable syringe is recycled, resold and reused. The reuse of the syringe causes the transmission of diseases, such as hepatitis B and acquired immune deficiency syndrome (AIDS).
In recent years, as indicated by some experts, the danger level of the medical staff suffered the occupational infection depends on the prevalence rate of the blood-borne disease among people. China is one of the countries having high incidence of hepatitis B, the number of the hepatitis B carriers is about 120 million, the infection rate of hepatitis C is up to 1.7%, and the prevalence of AIDS in China has already entered the period of rapid growth. Therefore, the medical staff in China is facing serious occupational exposure danger. Based on the results of questionnaire survey in 13 hospitals in Beijing, 1111 needles stabs occur to 432 probationer nurses in 10 months, i.e., it is 2.6 times per nurse per month in average, and due to the accidental injury, some nurses have been infected by blood-borne diseases, such as hepatitis B and AIDS.
For using the disposable syringe safely, and completely solving the cross-infection and the occupational exposure of the medical staff caused by the reuse of the disposable syringe, at the end of the last century, the World Health Organization (WHO) has proposed concepts such as safe injection, harmless to people being injected, and no risk to the medical-care staff. China has dedicated to develop and popularize the safe self-destructive syringe since 2000.
A good utility model or an invention should have the following advantages, such as having a low manufacturing accuracy, being easy to manufacture, being suitable for automated machine assembly, having a stable quality control in mass production. The safe self-destructive syringe that is commercial available presently has the following disadvantages.
A component of a retraction assembly (corresponding to a “conical connector assembly”) for cooperating with an inner wall of a front end of a barrel to locate the retraction assembly is mostly designed as an integral loop structure or a small supporting jaw, the loop structure has a small expanding angle and the supporting jaw has a small body force, both of which may cause a low firmness of the location between the retraction assembly and the inner wall of the front end of the barrel, thereby causing a risk of the self-retraction of the retraction assembly during the injection process.
The retraction assembly has no shockproof design, thus the shock during the long-distance transportation may also cause the risk of the self-retraction of the retraction assembly.
The head of the barrel has no member for preventing the retraction assembly from being overly pushed forward or has too small force to prevent the retraction assembly from being pushed forward, such that in practical assembly process, the retraction assembly may be pushed out of the opening at the head of the barrel due to an excessive assembly force, thereby causing assembly problem.
In the retraction assembly, a conical connector, for assembling a syringe needle, and a structural member, for cooperating with the inner wall of the front end of the barrel to locate the retraction assembly, are formed integrally, and the locating structure is designed as a small supporting jaw. So that, firstly, a mould manufacturing accuracy is too high, the manufacture is difficult and the product fraction defective is high, and secondly, each mould has less cavities (for an injection machine of 180 tons, each mould can only produce 32 parts), thus the mass production is not suitable.
There is no sealing ring provided between the retraction assembly and the inner wall of the barrel, which may cause the leakage problem; or the sealing ring is provided, however due to the complicated design structure of the retraction assembly, the assembly of the sealing ring is difficult, thereby causing the conventional syringe having a low adaptability for automation and being not suitable for mass production with the automatic assembling machine.
The design of the retraction mechanism also has disadvantages. The conventional retraction mechanism mostly uses a three or more sequential retractions, which are formed in this way, the retracting force of the plunger is transmitted to a corresponding part, and then is transmitted to another corresponding part or to more corresponding parts via the first corresponding part, thus may cause a risk of unstable retraction operation.
Further, mostly there is no retraction restricting mechanism in the inner wall of the rear end of the barrel, such that if the medical staff operates carelessly, the needle tip may be retracted excessively to be pulled out, which may cause other accidents.
Due to above disadvantages, presently the safe self-destructive syringe has not been rapidly and widely used in China yet. Therefore, it is important to provide an easily manufactured and highly safe disposable syringe for improving the medical safety of China.